1. Field of the Invention
This invention relates to hand tools in general, and more specifically to a gripping and locking plier or wrench of the vise-grip class.
2. Related Art
This invention is an improvement over the hand tools contained in a number of prior patents, the most predominant and successful being that of Petersen, U.S. Pat. No. 2,280,005, issued Apr. 14, 1942. This tool was called a vise-grip and has been on the market for over 50 years without any serious challenge as to its manner of construction and operation.
The vise-grip tool and various copies of it have several disadvantages, however, and many attempts have been made to eliminate these disadvantages but to date there has been little, if any, success in doing so.
The most serious problem has to do with the adjustment of the jaws to a work piece prior to locking. In order to understand the problem, one must first understand how the jaws are adjusted in the original Petersen tool, which is still used today. The adjustment mechanism includes a manually operated threaded screw that is turned clockwise to open the jaws wider and counter-clockwise to narrow the jaw opening. This screw extends axially inside an elongated hollow handle and has a knurled head protruding from the end of the handle, and the other end of the screw contacting one end of a fulcrum bar which is attached at its opposite end to a pivotable locking lever, or pivoting handle as it will be called herein for purposes of simplicity, and which in turn is attached to an adjustable jaw. The adjustable jaw pivots toward or away from a fixed jaw on the fixed handle. To adjust the tool to a work object, it is held in one hand while the other hand turns the screw head, thereby pivoting the adjustable jaw in a scissor-like fashion either toward or away from the fixed jaw. In order for the jaws to be locked on a work piece, the position of the adjustable jaw is very limited and critical to the locking operation as both jaws cannot be put into contact with the work piece at the same time and still be able to lock them. If such contact is made, they are too close for the lock to be activated; and by the same token, if the adjustable jaw is too far away from the work piece, the jaws still cannot be locked on the work. Therein lies the problem. In order to obtain this critical adjustment of the pivotable jaw, the adjusting screw must usually be adjusted several times before the proper adjustment can be achieved. This fine adjustment is required to lock the jaws every time a different sized work piece is involved.
A second disadvantage is that both hands must be used in order to adjust the tool so that it may be locked on a work piece as described above.
A third disadvantage is that both hands must also be used to release the jaws from a locked position, and if the lock is very tight, the release trigger becomes very difficult to operate. When it finally is activated, the handles will fly apart with considerable force and with possible injury to the operator.
A fourth disadvantage is that the adjustable jaw pivots in an arc and "scissors" as is mentioned above instead of moving in a linear direction. As a result, there is only one point at each adjusted position where the jaws are actually parallel to effect the best grip on a work piece, and it also limits the range of the jaw gap.
Still another disadvantage is the fact that when a vise-grip type tool is adjusted to where the adjustable jaw is at or near its most wide open point, the fixed handle and pivoting handle are so far apart as to be unreachable for the span of an average hand, again requiring the second hand to assist in bringing them together.